1. Field of the Invention
This invention is directed to novel compositions comprising one or more hexamantanes. This invention is also directed to novel processes for the separation and isolation of hexamantane components into recoverable fractions from a feedstock containing at least a higher diamondoid component which contains one or more hexamantane components.
References
The following publications and patents are cited in this application as superscript numbers:
All of the above publications and patents are herein incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference in its entirety.
2. State of the Art
Hexamantanes are bridged-ring cycloalkanes. They are the face-fused hexamers of adamantane (tricyclo[3.3.1.13,7]decane) or C10H16. The compounds have a xe2x80x9cdiamondoidxe2x80x9d topology, which means their carbon atom arrangement is superimposable on a fragment of the diamond lattice (FIG. 1). Hexamantanes possess six of the xe2x80x9cdiamond crystal unitsxe2x80x9d and therefore, it is postulated that there are thirty-nine possible hexamantane structure (FIG. 2). Among them, twenty-eight of the thirty-nine have the molecular formula C30H36 (molecular weight 396) and of these, six are symmetrical, having no enantiomers. Ten of the thirty-nine hexamantanes have the molecular formula C29H34 (molecular weight 382), and the remaining hexamantane is fully condensed having the molecular formula C26H30 (molecular weight 342), at times referred to as xe2x80x9ccyclohexamantane.xe2x80x9d
3 McKervey, Synthetic Approaches to Large Diamondoid Hydrocarbons, Tetrahedron, 36:971-992 (1980). 
7 Balaban et al., Systematic Classification and Nomenclature of Diamondoid Hydrocarbonsxe2x80x94I, Tetrahedron. 34, 3599-3606 (1978). 
Very little published work is available for hexamantanes and higher molecular weight diamondoids. Hexamantanes have not been artificially synthesized and these compounds have been recently thought only to have a theoretical existence.1,7 Academic chemists have primarily focused research on the interplay between physical and chemical properties in lower diamondoids such as adamantane, diamantane and triamantane. Adamantane and diamantane, for instance, have been studied to elucidate structure-activity relationships in carbocations and radicals.3 Process engineers have directed efforts toward removing lower diamondoids from hydrocarbon gas streams.2 These compounds cause problems during the production of natural gas by solidifying in pipes and other pieces of equipment.
The literature contains little information regarding the practical application of hexamantanes. This fact is probably due to extreme difficulties encountered in their isolation and due to failed synthesis attempts. Lin and Wilk, for example, discuss the possible presence of pentamantanes in a gas condensate and further postulate that hexamantane may also be present.1 The researchers postulate the existence of the compounds based on a mass spectrometric fragmentation pattern. They did not, however, report the isolation of a single pentamantane or hexamantane. Nor were they able to separate non-ionized components during their spectral analysis. McKervey et al. discuss an extremely low-yielding synthesis of anti-tetramantane.3 The procedure involves complex starting materials and employs drastic reaction conditions (e.g., gas phase on platinum at 360xc2x0 C.). Although one isomer of tetramantane, i.e. anti-, has been synthesized through a double homologation route, these syntheses are quite complex reactions with large organic molecules in the gas phase and have not led to the successful synthesis of other tetramantanes. Similar attempts using preferred ring starting materials in accordance with the homologation route, have likewise failed in the synthesis of pentamantanes. Likewise, attempts using carbocation rearrangement route employing Lewis acid catalysts, useful in synthesizing triamantane and lower diamondoids have been unsuccessful to synthesize tetramantanes or pentamantane. Hexamantanes have also failed like synthesis attempts.
1 Lin, et al., Natural Occurrence of Tetramantane (C22H28), Pentamantane (C26H32) and Hexamantane (C30H36) in a Deep Petroleum Reservoir, Fuel, 74(10):1512-1521 (1995) 
2 Alexander, et al., Purfication of Hydrocarbonaceous Fractions, U.S. Pat. No. 4,952,748, issued Aug. 28, 1990 
3 McKervey, Synthetic Approaches to Large Diamondoid Hydrocarbons, Tetrahedron, 36:971-992 (1980). 
7 Balaban et al., Systematic Classification and Nomenclature of Diamondoid Hydrocarbonsxe2x80x94I, Tetrahedron. 34, 3599-3606 (1978). 
Among other properties, diamondoids have by far the most thermodynamically stable structures of all possible hydrocarbons that possess their molecular formulas due to the fact that diamondoids have the same internal xe2x80x9ccrystalline latticexe2x80x9d structure as diamonds. It is well established that diamonds exhibit extremely high tensile strength, extremely low chemical reactivity, electrical resistivity greater than aluminum trioxide (Al2O3) and excellent thermal conductivity.
In addition, based on theoretical considerations, the hexamantanes have sizes in the nanometer range and, in view of the properties noted above, the inventors contemplate that such compounds would have utility in micro- and molecular-electronics and nanotechnology applications. In particular, the rigidity, strength, stability, variety of structural forms and multiple attachment sites shown by these molecules makes possible accurate construction of robust, durable, precision devices with nanometer dimensions. The various hexamantanes are nanometer sized three-dimensional structures showing different spacial arrangements. This translates into a variety of rigid shapes and sizes for the thirty-nine hexamantanes. For example, [12121] hexamantane is rod shaped, [121(3)4] hexamantane is xe2x80x9cTxe2x80x9d shaped, while [12134] is xe2x80x9cLxe2x80x9d shaped and [1(2)3(1)2] is flat with four lobes. The two enantiomers of [12131] are left and right-handed screw like structures. A variety of other shapes exist among the hexamantanes which may serve in applications which depend upon specific geometries. It has been estimated that MicroElectroMechanical Systems (MEMs) constructed out of diamond should last 10,000 times longer then current polysilicon MEMs, and diamond is chemically benign and would not promote allergic reactions in biomedical applications.6 Again, the inventors contemplate that hexamantanes would have similar attractive properties. Furthermore, some of the isomers of hexamantane (molecular weight 396 and 382) possess chirality, offering opportunities for making nanotechnology objects of great structural specificity and ones which have useful optical properties. Applications of these hexamantanes include molecular electronics, photonic devices, nanomechanical devices, nanostructured polymers and other materials.
6 Sandia National Laboratories (2000), World""s First Diamond Micromachines Created at Sandia, Press Release, (Feb. 22, 2000) www.Sandia.gov. 
Notwithstanding these advantages of hexamantanes, the art, as noted above, fails to provide for compositions comprising hexamantanes or for processes that would lead to these compositions. In view of the above, there is an ongoing need in the art to provide for compositions comprising one or more hexamantanes.
This invention is directed to novel compositions comprising one or more hexamantane components.
Accordingly, in one of its composition aspects, this invention is directed to a composition comprising one or more hexamantane components wherein said composition comprises at least about 25 weight percent hexamantane components based on the total weight of the diamondoids in the composition with the proviso that when only a single hexamantane is present than that hexamantane is not the fully condensed unsubstituted hexamantane component, unsubstituted cyclohexamantane, which has the molecular formula C26H30.
In another of its composition aspects, the compositions preferably comprise one or more hexamantane components wherein the hexamantane components make up from about 50 to 100 weight percent, preferably about 70 to 100 weight percent, more preferably about 90 to 100 weight percent and even more preferably about 95 to 100 weight percent hexamantane components based on the total weight of the diamondoids in the composition with the proviso that if only one hexamantane compound is present it is not the fully condensed unsubstituted hexamantane, unsubstituted cyclohexamantane.
In another of its composition aspects, the compositions comprise at least about 10 weight percent and preferably at least about 20 weight percent of hexamantanes based upon the total weight of the composition with the above proviso that said single hexamantane compound is not the fully condensed unsubstituted hexamantane. Other compositions of this invention, with this proviso, contain from 50 to 100 weight percent, 70 to 100 weight percent, 95 to 100 weight percent and 99 to 100 weight percent of hexamantane based upon the total weight percent of the composition.
In another of its composition aspects, the compositions comprise from about 70 to 100 weight percent, more preferably from about 90 to 100 weight percent, even more preferably from about 95 to 100 weight percent and most preferably from about 99 to 100 weight percent of a single hexamantane component, including isolated optical isomers thereof, based upon the total weight of the composition, all with the proviso that said single hexamantane compound is not the fully condensed unsubstituted hexamantane, cyclohexamantane.
When such compositions are sufficiently enriched in hexamantane components the hexamantanes can form crystal structures. Accordingly, another aspect of this invention is directed to a composition comprising a hexamantane crystal with the proviso that when there is only a single hexamantane component, then it is not the fully condensed unsubstituted cyclohexamantane. Since such hexamantane can co-crystallize, another aspect of this invention is directed to the co-crystals comprising crystals of at least two hexamantane components.
This invention is also directed to novel processes for the separation and isolation of hexamantane components into recoverable fractions from a feedstock containing hexamantane components and nonhexamantane materials These processes for recovering a composition enriched in hexamantane components entail removing at least a portion of the components which have a boiling point below the lowest boiling hexamantane component and utilizing a subsequent separation technique to recover hexamantane components from the resulting residue. Accordingly, this aspect is directed to processes which comprise:
a) selecting a feedstock comprising recoverable amounts of hexamantane components and nonhexamantane materials;
b) removing from the feedstock a sufficient amount of nonhexamantane materials having a boiling points below the lowest boiling point of hexamantane component in the feedstock under conditions to form a treated feedstock enriched in hexamantane components which can be recovered;
C) recovering hexamantane components by separating said treated feedstock formed in b) above with one or more additional separation techniques selected from the group consisting of chromatographic techniques, thermal diffusion techniques, zone refining, progressive recrystallization and size separation techniques.
In a preferred embodiment, after the step recited in b) the treated feedstock can be thermally treated to pyrolyze at least a sufficient amount of nondiamondoid components therefrom under conditions to provide a thermally treated feedstock retaining recoverable amounts of hexamantane. Such a pyrolization step prior to step c) is useful for thermally degrading at least a portion of any materials remaining in the treated feedstock having a thermal stability lower than the hexamantane components. This pyrolysis step can be carried out before step b), if desired.